1. Field of the Invention
The present invention relates to a ceramic-resistor heating plate, more particularly, to a ceramic-resistor heating plate, which can prevent the problem of corona discharge.
2. Description of the Prior Art
The ceramic-resistor heating plate uses the infrared radiation to heat the object to be heated. Therefore, the ceramic-resistor heating plate is safer than the convention heater with real fire. However, since the ceramic-resistor heating plate is generally energized by electric power, the spark-induced problem, such as the burning of flock attached to the ceramic-resistor heating plate, is liable to occur. To prevent the above-mentioned problem, the distance between the electrodes of the ceramic-resistor heating plate is required to exceed 2.5 mm-3.0 mm to prevent the corona discharge and spark problem.
FIGS. 1, 2 and 3 show the structure of the conventional heating plate in an electric heater. The heating plate comprises a wave-shaped conductive fin plate 11, a ceramic-resistor heating body 12 sandwiched therebetween, lateral frame 13, and cover 14. The connector 15 protruded from the cover 14 conducts electric power to the heating body 1 through the fin plate 11. The front side and back side of the heating body 12 are coated with conductive film 121 and 122, respectively, for conducting the electric power from the connector 15. As shown in FIG. 3, the distance between the two electrodes (terminals) 110 of the heating body is required to be at least 3 mm to maintain the allowable voltage of the heating body. Therefore, the thickness of the heat body is increased. However, the material is wasted and the power consumption is increased. From the formula, R=.rho..multidot.L/A, for a fixed value of resistivity .rho., the resistance R is proportional to the length L and inversely proportional to area A. The increase of heating body thickness will increase the resistance thereof. Therefore, to make a thinner heating body and maintain normal operation thereof within allowable voltage range is an important design issue.